1. Field of the Invention
The invention relates to the field of electronic circuit component cards having edge connectors for mating with corresponding slot connectors, such as peripheral component interconnect (PCI) cards which are pluggable into PCI slot connectors disposed on computer motherboards and backplanes, for example.
2. Background Information
Various electronic circuit component cards, also referred to as electronic cards and card devices herein, having edge connectors for mating with slot connectors on personal computer (PC) system motherboards and/or backplanes, for example, are known. These cards are generally classified by the bus type they are designed for, and a number of standard bus/card/connector types are currently in use. These standard types include ISA (Industry Standard Architecture--8/16 bits) and EISA (Expanded ISA--32 bits), SCSI (Small Computer System Interconnect), PCI (Peripheral Component Interconnect), MCA (Micro Channel Architecture), VLB (VESA Local Bus), AGP (Accelerated Graphics Port), and USB (Universal System Bus), to name just a few.
The card edge connectors typically have a number of relatively closely spaced metal contacts on one or both sides of the card edge, and the corresponding slots similarly have a like number of closely spaced metal contacts therein. When the card edge connector is inserted in the slot connector, the corresponding contacts make electrical connection. Through these contacts and their electrical connection, the card device and the personal computer system communicate data, address and control signals, for example. The card device also generally obtains electrical energy from the personal computer system through two or more of the contacts.
The card edge connectors have a predefined size and, in the case of PCI cards, for example, have key slots which align with corresponding key ridges provided within the slot connectors. These keyed features, as well as the fact that the slots of the slot connectors are closed at ends thereof, help to ensure that the card edge connector contacts align with the correct slot connector contacts when fully inserted. However, these card devices are generally designed with the assumption that they will be inserted by hand by the personal computer owner or technician. During insertion by hand, it is possible that there could be a momentary contact with an adjacent card or other nearby component, or there could be a momentary misalignment of the closely spaced edge contacts, causing a short circuit, for example. (It should be noted that the providing of the keyed features generally adequately prevents any contact misalignment during insertion.) Because of this, such cards are generally installed with the personal computer system turned off, i.e., "powered down."
The focus of the following discussion will be PCI-based card devices, however, the same factors addressed hold true for other types of card devices. The PCI bus is a synchronous, processor independent, 32- or 64-bit bus that functions similarly to a processor local bus. The PCI bus can be thought of as a buffered intermediate or so-called mezzanine bus, that is, an extension of the processor local bus. It is coupled to the personal computer processor local bus by so-called "bridge" circuitry, but maintains its own separate set of circuits. The original PCI bus specification required a constant speed of 33 MHz, which translates to a transfer rate of 80-120 Mbs in a 32-bit environment, and up to a 264 Mbs transfer rate in a 64-bit environment. The PCI bus operates on 5 volts, 3.3 volts, or both.
PCI and the other so-called local bus technologies, e.g., VESA (Video Electronics Standard Association), were developed to permit personal computers to communicate more quickly with peripheral devices, particularly video cards in the case of VESA where the "V" stands for video. Graphic operating systems and applications, for example, place a high throughput demand on a bus system. The original IBM PC (IBM is a registered trademark of International Business Machine Corporation) had a bus speed of about 1 megabyte per second, the IBM AT about 4 megabytes per second, a typical ISA bus about 8 megabytes to a maximum of 16 megabytes per second, the EISA bus has 32 megabytes per second, the MCA bus 20-40 megabytes per second, the VESA VL-1 has 20-132 megabytes per second, the VESA VL-2 up to 264 megabytes per second, the PCI 1.0 has 80-120 megabytes per second and the PCI 2.0 up to 264 megabytes per second. The VESA and PCI buses are called "local bus" technologies because the motherboard bus is bypassed, and the peripheral connected to the processor "local" bus, through the VESA circuitry or the PCI bridge circuitry. This permits peripherals to be run at the full CPU clock speed, over the full CPU 32- or 64-bit data path, with readily apparent benefits.
The PCI standard bus was also developed as a way to integrate peripherals in general onto personal computer motherboards. PCI buses have gained favor over other buses due in part to the fewer control lines used. A PCI bus uses 32 conductors to carry both the address and data lines, while a VESA VL-1 bus, for example, uses up to 64 (32 data and 32 address). This permits PCI cards to be, in general, smaller than other types of local bus cards.
For these reasons, and others, PCI buses, cards and card slots have become widespread in the personal computer (PC) market, and there are now a plethora of PCI-based card devices available. Until recently, personal computer buses and card devices, e.g., PCI buses and card devices, have not been used in mid-range to high-end, e.g., "mainframe," computer systems. Therefore, until recently, only the personal computer user has had the advantage of the wide range of available peripheral component interconnect (PCI) card devices, and the like. However, as personal computers and their peripherals have reached higher and higher performance levels, and have become more and more varied, their integration into mid-range to high-end computer systems has been given serious consideration. It has now been recognized that the users of mid-range to high-end computer systems could benefit from the variety, versatility and availability of PCI card devices, and the like.
Therefore, a need existed for a way to accommodate these PCI card devices, and the like, in mid-range to high-end computers. Mid-range and high-end computer systems are now being shipped with PCI card devices. One example of a mid-range computer is the IBM AS/400 series (AS/400 is a registered trademark of International Business Machine Corporation).
While providing a PCI bus and card connector on a mid-range to high-end computer system motherboard or backplane, for example, to meet the above-identified need may seem to be relatively straight forward, and admittedly, can be accomplished with sufficient effort, there are a number of related technical issues which have to be addressed in doing so. One of these issues relates to common differences in the way personal computers and mid-range to high-end computers are put to use, as will be explained.
PCI and similar electronic card devices generally derive power from the personal computer motherboard or backplane through the card slot they are plugged into. Further, it is generally assumed in the design of the cards that they will be plugged in by hand when the power to the personal computer is off, to avoid the possibility of damage to components on the cards and/or motherboard, should there be a momentary contact with an adjacent card or component, or a misalignment of the closely spaced contacts, during insertion causing a short circuit or connection of power to the wrong contact, for example, as mentioned earlier.
This requirement that power be off during insertion and/or extraction of the card is inconvenient but generally tolerable when the card devices are used in the typical desktop personal computer. Because PCI and other types of card devices designed for personal computers are not designed to be able to be plugged in while the computer system is powered up, until now, their use in high-end and mid-range computer systems could have undesirable consequences.
In mid-range to high-end systems, uninterrupted service is highly desirable and therefore, it is also desirable to be able to "hot plug" peripheral devices and their controller cards, that is, plug them in and take them out without turning off the power to the computer system. This is sometimes referred to as "concurrent maintenance." Since such computer systems typically are used to perform critical business functions, for example, the losses in productivity and the resultant economic costs associated with computer system down-time can be significant. Such systems may be serving many users concurrently.
Besides the desire for uninterrupted service, there may be considerable penalties involved with powering-down and powering-up such computer systems to add or replace components. For example, currently running programs must be halted and sometimes large amounts of data saved to non-volatile storage, before the system can be powered down without risking data loss. In mid-range and high-end computer systems, considerable amounts of time and inconvenience may thus be involved in performing unscheduled shutdown and restart operations in an orderly fashion.
In personal computer systems, the above are generally not significant factors to be considered when a new card device is to be added or when an existing card device requires service or replacement. Powering down and restarting a PC does not generally cause the concern it would cause for a user of a mid-range to high-end computer system since, with some exceptions, these are relatively quick and simple operations. Providing uninterrupted customer service even when a system is being upgraded or components repaired is highly desirable and may even be essential for commercial viability in mid-range to high-end systems due to the factors mentioned above. However, this is generally not a major concern with a typical desk-top PC since the PC is not typically performing as critical a business function.
Therefore, in order to take advantage of the multitude of circuit cards, e.g., PCI cards, designed for personal computers, in a mid-range to high-end computer system, without incurring disadvantageous system down-time, a need has existed for a way to safely hot-plug PCI card devices in a mid-range to high-end computer system, avoiding the danger of contact with powered-up adjacent cards or components, for example. This need is met by the autodocking assembly and method described and disclosed herein.
At this point, it should also be mentioned that besides the autodocking assembly and method described herein which prevents accidental contact with adjacent cards or component, in order to achieve hot-plugging, there may be other engineering issues involved. For example, it may be necessary or desirable to place unused slots in a quiescent powered-down state until a card device is plugged therein. This serves to avoid transients, for example, which may occur as the electrical connection is made between the slot and card edge contacts. Since no two metal contact surfaces are perfect, when they are mechanically brought together, there may initially occur what is commonly called "bounce," i.e., a momentary making and breaking of electrical connection, until the contact surfaces are securely aligned. Such bounce can result in electrical noise which could be misinterpreted as data or control signals, for example. Further, some electronic components may not tolerate the power spikes which could result from this bounce. In an IBM proprietary solution, the bus slot is kept quiescent until it is detected that a card device is seated therein, at which point power can be safely applied to the slot connector and associated card device. Therefore, it should be understood that additional engineering issues may need to be addressed in order to use the present autodocking assembly and method in a given situation, i.e., with a particular slot/card electrical configuration.
Although typically the factors making hot-pluggability highly desirable in mid-range to high-end computer systems are not as relevant to PCs, there may be a number of exceptions. In recent years, desktop personal computers have become more and more powerful, and have even been adapted to operate as network servers, and the like, for small businesses. In such a role, there are the same kind of penalties for down time as with mid-range to high-end computer systems.
Therefore, a need has also existed for a way to safely hot-plug PCI cards, and the like, in personal computer systems, especially those used as network servers and the like.
Within the International Business Machines Corporation, there have been some efforts at providing circuit board autodocking before, referred to here as "above the card solutions." However, PCI cards, and the like, sometimes not only have bottom edge connectors for mating with corresponding PCI motherboard/backplane slots, but also have top edge connectors for connections to other components. The previous above the card solutions did not accommodate these top edge connectors. Therefore, a need has existed for an autodocking design which would permit connectors on the top edge as well as the bottom.
It is also noted that these prior above the card solutions used a number of component parts, complicating assembly and manufacturing, and that these solutions generally would not work with a variety of types of cards. Therefore, a need existed for an autodocking design which reduced the number of parts and could accommodate a number of different cards.